1. Field of the Invention
The present invention relates to support assemblies which electrically and structurally attach semiconductor devices to circuit boards. In particular, the present invention relates to support assemblies which orient semiconductor devices perpendicularly relative to circuit boards. Preferably, the support assembly of the present invention is readily installable upon, removable from, and reinstallable upon a circuit board.
2. Background of Related Art
The use of support boards for mounting semiconductor dice to a circuit board is known. Many support assemblies include electrically conductive leads which extend therefrom. The leads establish an electrical connection between the bond pads of the die and the corresponding terminals on a circuit board. Exemplary devices are described in the following U.S. Pat. Nos. 5,484,965 (the "'965 patent"), issued to Gerard A. Woychik on Jan. 16, 1996; 5,581,877 (the "'877 patent), issued to Gerard A. Woychik and John C. Mather on Dec. 10, 1996; 5,451,815 (the "'815 patent"), issued to Norio Tanaguchi et al. on Sept. 19, 1995; 5,266,833 (the "'833 patent"), issued to David G. Capps on Nov. 30, 1993; 4,992,849 (the "'849 patent"), issued to Tim J. Corbett and Alan G. Wood on Feb. 12, 1991; and 4,992,850 (the "'850 patent"), issued to Tim J. Corbett and Alan G. Wood on Feb. 12, 1991.
Due to their permanent attachment to a circuit board, many single inline package devices are somewhat undesirable. Many single inline package devices attach to a circuit board by an electrically conductive bond, such as solder. Other single inline packages are attached to a circuit board with permanent bonding materials such as epoxy or acrylic. Thus, users cannot readily remove and replace such devices. Further, some single inline packages include multiple integrated circuits attached thereto, making them somewhat undesirable because a user could not readily replace one bad die on such a device.
Some vertically mountable support assemblies have multiple laminated layers. The thickness of many such devices causes them to consume a significant amount of area on a circuit board. The '815 patent discloses one such device, wherein leads extend from the bottom of the device in more than one plane. The illustrated device has four layers and four corresponding rows of leads extending from the bottom thereof.
Other vertically mountable die support assemblies include electrical contacts on more than one edge thereof. This configuration is somewhat problematic in that each of the edges of such devices must communicate electronically with a circuit board. Consequently, a user's ability to remove and replace such devices is hindered. An exemplary device is described in the '833 patent.
Moreover, the interposers of the '833 patent are insertable into a socket which creates an interference fit between each electrical contact on the device and an electrical trace on the socket. However, it would be difficult to insert such a support structure into a base which exerts sufficient pressure on all four sides of the die to establish and maintain an adequate interference contact between the bond pads and the electrical connections. Furthermore, the amount of circuitry that would be required to establish an electrical connection between a circuit board and contacts which are distant therefrom would impart such a device with a relatively high impedance and slow the overall speed of a system which includes such a device.
Thus, a vertically mountable interposer is needed which is readily removable from and replaceable upon a carrier substrate. An interposer with good heat dissipation and reduced pitch limitation is also needed. There is also a need for a thin, flat interposer which protects an attached semiconductor device and any associated devices that are also attached to the interposer.